Wireless telegraph and telephone transmission



Dec. 8 1925;

H. J. ROUND WIRELESS TELEGRAPH AND TELEPHONE TRANSMISSION Filed March 31, 1920 Patented Dec. 8. 1925.

UNITED STATES PATENT OFFICE.

HENRY JOSEPH ROUND, OF LONDON, ENGLAND, ASSIGNOR TO THE RADIO CORPORA- TION OF AMERICA, 01 NEW YORK. N. Y. A CORPORATION O F DELAWARE.

WIRELESS TELEGRAPH AND TELEPHONE TRANSMISSION.

Application filed March 31, 1920. Serial No. 870,174.

To all whom it may concern:

Be it known that I, HENRY J osnrn ROUND, a subject of the King of Great Britain, residing at 9 Woodberry Crescent, Muswell Hill, London, England, have invented new and useful Improvements in Wireless Telegraph and Telephone Transmission, of which the following is a specification.

This invention relates to improvements in or relating to valve and other interrupting devices used in wireless tele raph and telephone transmission and its 0 ject is to reduce the internal heating that occurs in such devices during use.

I The invention is illustrated by the accompanying drawing of which Figs. 1 and 2 illustrate the nature of currents, Fig. 3 shows a wireless transmitter, Figs. 4 and 5 illustrate voltages. Fig. 6 illustrates a current: Figs. 7 and 8 show alternative arran ements of transmitter and Fig. 9 shows a telephone transmitter.

It is found that if it can be so arranged that the current issuing from the device is of an intermittent nature somewhat of the form shown in Figure 1 of the accom anying drawing, and theamplitude is sultably chosen then nearly the whole of the energy supplied by a direct current source can by the aid of arrangements described below be expended externally to the device.

lVhen no current is flowin there is no loss 'in the deviceand when maximum current is flowingthe loss is-small because the voltage drop .across the device is very small. By producing a square form current i. e. a current somewhat of the nature shown in Figure 1, it is possible to pass rapidly from one state of" minimum loss to the other state of minimum loss.

According to this invention a control voltage of a square form is applied to a valve or other interrupting device and arrangements are made for the absorption or taking up of the energy developed in the higher harmonics.

In the case of a valve, for instance, .the first of these conditions may be effectively produced by shunting the grid coil by a low resistance valve of the F eming type with suitable E. M. F. adjustment and the second by inserting in the anode circuit one or more suitably damped oscillatory circuits tuned to the first harmonic or to the first and other harmonics and usually in series with the 'main or fundamental circuit.

Alternatively it is possible to replace the absorbing action of the combination of harmonic circuits by a resistance in series with a rejector tuned to the fundamental.

Also it is possible to obtain the effect in certain cases by means of absorption harmonic circuits in series and a fundamental circuit in parallel or vice versa- In actual practice both the above conditions may be produced to some extent'aw tomatically, the first by taking advantage of the rectifying properties of the mam valve grid and the second by the distributed impedance of the anode circuit such as when that circuit is artly formed of an aerial system. The e ect is, however, much more pronounced and the resulting reduction in internal heating so much the reater when special arrangements are ma e as in the manner detailed above.

The invention may be illustrated by comparison with a simple make and break commutator with equal spaces and bars; the valve being represented by a commutator in series with oscillatory circuits and a direct current source. With a proper series of circuits a commutator "so arranged will be sparkless, in other words there will be no loss in the commutator.

hen it is desired to vary the amplitude of the fundamental, say, by means of the voice, then the form of the grid voltage is varied so that the maximum amplitude remains constant while the duration of maximum E. M. F. in each period varies, that is to say, the form varies from that shown in Figure 1 to that shown in Figure 2, and the loss in the valve remains a minimum.

One of the methods by which this type of variation is provided by the voice is to apply to the subsidiary low resistance valve ment oned above in addition to the sine form alternating E. M. F. a voltage controlled by a microphone.

Consider the e'flect of the summation of 'the low frequency voltage due to the miositive pulses to the grid of the 4 main valve are reduced both in amplitude and in width, while if the high frequency voltage is very ositive, the positive pulses are increased bet in amplitude and in width. If, however in addition a limiting voltage device, such as a low resistance Fleming valve be applied across the high frequene E. F., the result will be t at the big fre uency positive pulses applied to the grid of t e main valve will not var in amplitude but only in width. The amplitude should be so chosen that the valve, as before, is taken very ra idly from one state of minimum loss to t e other. It will readily be understood that although the amplitude of the aplied voltage is constant the variations prouced by t e voice in the width of the positive ulses will cause variations in the amlitu e of the fundamental wave produced 1n the anode'circuit.

In Figure 3 of the drawing is shown agenerating or amplifying valve V havin its grid connected to an oscillatory circuit in which high freguency oscillations are generated by an in ependcnt generating circuit G. Across the grld and filament of valve V is arranged a low resistance Fleming valve 4; with an adjusting battery B so that if the voltage applied to circuit 0 from circuit G is of the form shown in Figure 4 the voltage across grid and filament of valve V willhave the form shown in Figure 5, but as the lower portions of this last curve are inoperative, the form of the anode current will be as shown in Figure 6. In the anode circuit besides the oscillatory circuit F tuned to the fundamental frequency and coupled to an aerial A are two other circuits F F tuned to the third and fifth harmonics.

In place of employing an independent generating circuit an interaction may be arranged between the circuits F and O as shown in Figure 7 Figure 8, shows in place of the circuits F, F, of Figure 3 a resistance rod 9 in series with a rejector circuitR tuned to the fundamental frequency.

Figure 9 shows one method of adapting the invention to telephony: here the circuits are the same as in Figure 3 but a microphone circuit M is connected through a transformer T to the grid filament circuit of the valve V. 1

What I claim is:

1. The method of wireless transmission which consists in applying to a thermionic valve a rapidly fluctuating voltage'of square wave form and absorbing outside the device the energy developed in harmonics of the fundamental frequency.

I J 2. In a wlreless transmitter, the comblnation of an interrupting device, means for 1mpressing upon it a rapidly fluctuating volt-.

age of square wave form and means for absorbing the energy developed in harmonics of the fundamental frequency.

3. In a wireless transmitter the combination of a three-electrode valve, means for impressin upon it a square wave form voltage an means for absorbin the energy developed in harmonics of t e fundamental frequency. .a

4. In a wireless transmitter, the combination with a three-electrode valve having separate input and output" electrodes of an oscillatory circuit connected to the anode of the valve and tuned to the fundamental frequency of the current sup lied by the valve and a circuit tuned to a iarmonic of that frequency and connected to the anode of the valve. 7

5. In a wireless transmitter, the combination with a three-electrode valve having separate input and output electrodes of means for impressing upon it a fluctuating voltage of square wave form, an oscillatory circuit connected to the anode of the valve and tuned to the fundamental frequency of the current supplied by the valve and a circuit tuned to a harmonic of that frequency and connected to the anode of the valve.

6. A wireless transmission system including athree-electrode valve and means associated with said valve for producing a flat top wave form therein said means consisting of a two electrode valve in series with the grid and filament of the first valve.

7. In a wireless transmitter, the combination of a three-electrode valve, an oscillatory circuit connected to the grid and filament of the va1ve,-a two-electrode valve connected to the id and filament in parallel with the oseilatory circuit, a second oscillatory circuit connected to the plate and filament of the first valve and a third oscillatory circuit connected in series with the second circuit and tuned toa harmonic of the frequenc to which the second circuit is tuned.

8. 1X1 a wireless transmitter the combination of a three-electrode valve, an oscillatory circuit connected to the grid and filament, a two-electrode valve connected to the rid and filament in parallel with the oscill atory circuit, a transformer having its secondary winding connected between the two valves and a battery and microphone connected in series with the primary winding of the transformer.

HENRY JOSEPH ROUND. 

